Grant Vortex Condensing Combi 26 hot water problems

Discussion in 'Plumbing and Central Heating' started by didspip, 19 Feb 2011.

  1. didspip

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    I have a problem with my Grant Vortex condensing combi 26 Oil boiler.
    When I run the hot water for a bath after a few minutes the water runs luke warm, turn off the hot tap and wait a few minutes and it is hot again.
    It always used to work ok.
    The other thing I have noticed is I can hear air bubbles traveling around the heat exchanger pipes and the water store. the heating is ok and quiet.
    Its almost as if there is not enough water in the store?
    The boiler is only 4 years old but has had a few problems needing the boiler to be drained and re filled a number of times.
    Leaking washer on heat exchanger - leaking flow switch washer - leaking auto air vents and leaking filling loop taps.
    I have replaced the filling loop, air vents and washer on the exchanger.
    When I re fill the boiler via the filling loop does this also fill the water store?
    Any help as to the cool water issue would be appreciated.
     
  2. Terrywookfit

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    Have you checked the TMV?
     
  3. didspip

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    In what way? it is set ok
     
  4. moliver34

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    if its not the TMV; then more likely the pcb for the heat store is faulty.

    contact; www.grantuk.com

    ask to speak to the technical department who will be able to assist you.
     
  5. didspip

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    Thanks for the reply but can you tell me how I check the TMV? :?:
     
  6. didspip

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    Thanks for the info, can you explain why I hear air bubbling through the store and heat exchanger pipes when the hot water is running?
     
  7. oilhead

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    Check heat store AAV for operation. Is the cap open?
    Are there any manual vents on the pipework you can bleed?
    Is the DHW ht exchanger scaled? How does the flow of hot water compare to cold water flow?Is the flow pipe to the TMV hot when the tap starts to cool down?
     
  8. didspip

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    Thanks for the reply.
    AAV on heat store has been replaced and the cap is open but I never hear air coming out even when I drain the system and re fill? does the water in the store drain when the system is drained and re fill when I fill the system back up?
    All manual air vents have been bled.
    Four year old boiler, will the ht exchanger be scaled after this period? if so do I need to strip it out to check? clean or replace?
    Doesn't it use the ht exchanger for the central heating?
    As for the TMV flow pipe I will check that later when I run the bath and get back to you.
     
  9. didspip

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    I can confirm that The flow pipe to the TMV also cools down when the hot water cools down, normally it is too hot to touch.
    Does this mean the TMV is buggered?
     
  10. leakydave

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    What do the heating pipes do when you run hot water? Do they get hot even if the heating is off?
     
  11. oilhead

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    I can confirm that The flow pipe to the TMV also cools down when the hot water cools down, normally it is too hot to touch.
    Does this mean the TMV is b*****r?[/quote]

    No, it means that the problem is within the controls of the DHW operations.
    Does the burner start up when HW is demanded? Possible flow switch problem.
     
  12. Agile

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    With oil on the way out and prices rising daily why not consider an alternative fuel source?




    [​IMG]

    Anyone know why the picture will not display here? Click on the link until its corrected!
     
  13. didspip

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    No, it means that the problem is within the controls of the DHW operations.
    Does the burner start up when HW is demanded? Possible flow switch problem.[/quote]

    Burner starts up ok every time. Flow switch was replaced last year due to intermittant hot water. This gave hot then stone cold water and I could hear the relay clicking in and out. I have Hot then warm water with no relay clicks. When it runs warm if I turn the tap off for a minute or two it is back up to full temp.
    Yesterday as an experiment whilst running the bath I tapped the TMV lightly with a hammer thinking that if it is scaled up this may free it off. After this the hot in pipe stayed too hot to touch and this morning I ran a full bath without it going cold. Does this seem feasible or is it just a coincidence?
     
  14. manortim

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    What is the water in your area like for hardness or do you have a softener?

    What happens if you run the tap slowly?
     
  15. didspip

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    According to Anglian Water the water in my area is Vert Hard.
    I have had a bit of success using an un conventional method based around everyones advice that the TMV may be scaled.
    Whilst the bath was running I tapped the TMV with a small hammer, as I was doing this all of a sudden the hot in pipe became too hot to touch again, as it should. I was then able to run the full bath without heat loss whilst having the heating on.
    I think I may have dislodged some scale?
    Does this sound possible?
    When the boiler was installed nearly 4 years ago it was a cash barrow job and I suspect there was no inhibitor used.
    If so once I have replaced the TMV and the bleed valves again what is the best inhibitor to tackle limescale?
     

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